95 camaro overheating problems

its the 3.4 i belive. so we blew the heater core and bypassed it. the mixed orange and green together. im not sure if thats a problem? but its not wuite overheating but getting damn close to the 260 mark. its fine on the highway but at a light it heats up fast. and when im at idle or shut the car off coolant bleeds out of the overfill bottle. a good amount of it. anyone have any advise? thanks b

Mixing the orange and green can be bad!!

Did the motor overheat or run long after the heater core went?

Are your Cooling fans working. When was the last time you flushed the coolant. I personally run a Pro-Blend Coolant and have had good results with it. though it is not for winter use

it ran for about 2 days before we bypassed the heater core. so should i flush it?
my fans are working.